In Context

780 www.thelancet.com/neurology Vol 10 September 2011

Controlling machines with just the power of thoughtOnce just a science-fi ction notion, the idea of controlling machines with thought alone is now a reality. With the proof-of-concept phase in the past, researchers think that brain–computer interface technology should now move from the laboratory into people’s lives. Patricia Luna reports.

Incredible as it might sound, several dozens of people around the world can type on a keyboard, write an email, search the internet, move a wheelchair, or control a prosthetic arm just by thinking. Control of machines by thought has long captured the imagination of human beings, but this idea has only recently abandoned science-fi ction territory to become a proven reality.

Brain–computer interface (BCI) technology has great potential to change the everyday lives of people who are severely paralysed, improving quality of life and restoring function in people with motor disabilities. But despite the rapid growth and development of this emerging neurotechnology fi eld in the past few years, it remains mostly confi ned to the laboratory and has not yet made the transition to become a widely available technology for disabled people. What are the main challenges to overcome and what are the possible uses of BCIs and their future applications?

According to Jonathan Wolpaw, Professor and Chief of the Laboratory of Neural Injury and Repair at the Wadsworth Center, New York Department of Health and State University of New York, NY, USA, a BCI can be defi ned as “a system that measures central nervous system activity and converts it into artifi cial non-muscular outputs that act on the outside world or on the body”. Wolpaw has been working on BCI technology since its beginnings in the early 1980s.

By enabling paralysed people to interact with their environment with brain signals rather than muscles, BCIs could change the lives of extremely disabled people with disorders such as amyotrophic lateral sclerosis

(ALS), cerebral palsy, stroke, multiple sclerosis, or spinal cord injury. BCIs can provide some non-muscular communication in these patients and thus, to some degree, restore their functional independence and even their mobility.

The technology works by recording electrical brain signals—local fi eld potentials or neuronal action potentials (spikes)—from the scalp, the cortical surface, or within certain movement-controlling areas of the brain (eg, primary motor cortex, premotor cortex, or parietal cortex). The signals are analysed and translated into commands (output) that control applications, such as word processing or email programmes, or devices, for example wheelchairs or a robotic arm.

Two main options are available to measure the electrical fi elds that result from brain activity: non-invasive techniques that record activity from the scalp using electroencephalogram (EEG) systems; and invasive methods that place recording electrodes either on the cortical surface to record electrocorticographic (ECoG) signals, or within the brain to record local fi eld potentials or, uniquely, the activity of individual neurons. Non-invasive EEG does not require surgery and, with specifi c training, is quite simple to use. However, invasive methods have better topographical resolution and a wider frequency range. Although scientifi c debate about the advantages and disadvantages of each method is ongoing, both approaches have potential for the future.

Braingate is one of the most advanced invasive devices available, developed by John Donoghue, Professor of Neuroscience and Engineering, Director of the Brown Institute for Brain Science, Providence, RI, USA, and a pioneer in BCI, and by Leigh Hochberg, Associate Professor at Brown University. BrainGate uses a 4×4 mm array of 100 microelectrodes (the size of a baby aspirin). Donoghue explains: “When this is inserted in the brain (the motor cortex), the hair-thin electrodes pick up signals from one or a couple of neurons each.” The device allows people to type on a computer or move a cursor immediately with no training. “In the devices that are recording neurons, control is immediate because we are directly mapping the brain’s actual motor signals to the cursor motion—as if the hand were moving a mouse that moved the cursor”, Donoghue adds.

One of the most interesting features of BCI technology is that the user receives continual feedback about the results of the BCI’s output, which in turn aff ects the user’s brain activity and infl uences subsequent output. As such, this technology could help to answer fundamental questions about how our brains learn and adapt to new tasks and environments. “It is becoming increasingly evident that people using a BCI are developing a new skill. This is not a mind-reading device. If you have a robotic arm that you control with brain signals, its actions become the brain’s output and the brain is being constantly asked to adapt to it. Thus, BCI use is a new skill that must be mastered and maintained as with standard muscular skills, such as walking or talking”, explains Wolpaw.

José del Rocío Millán, Professor and Chair in the Non-Invasive

“It is becoming increasingly evident that people using a BCI are developing a new skill.”

For more on Braingate see http://www.braingate.com/

For more on The Wadsworth Center Brain–Computer

Interface System see http://www.wadsworth.org/bci/

index.html

For more on non-invasive versus invasive techniques see

IEEE Eng Med Biol Mag 2010; 29: 16–22

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Brain–Machine Interface Center for Neuroprosthetics at the School of Engineering in the Swiss Federal Institute of Technology Lausanne, Switzerland, agrees on this point: “The learning curve allows the device to adapt to the person using it and gives the user the ability to voluntarily modulate their brain activity.” Millán’s team is developing a wheelchair that allows people with severe paralysis to move independently, avoiding real life obstacles and sending commands that are executed in real time (in a 1-second frame) with good reliability. Patients need only a few hours of training before being able to operate the device. As Millán explains, “this learning process, called mutual learning, will allow the user to constantly modulate activity over time, so that decoding the signal becomes more reliable. The machine and the user learn from each other.” Their device operates with a shared control principle—ie, the machine and the user’s intelligence are integrated to collaborate towards achievement of the same aim. Both machine and user establish an interaction by which the person sends high-level commands and the machine undertakes all the low-level commands needed to execute those orders. “The level of assistance by the machine depends on the person’s precision in orders. The more precision, the less assistance the machine will provide and vice versa”, adds Millán.

Diff erent research groups around the world have proved that operation of BCI devices is possible. So why have these technologies not hit the high street? “BCI systems that control applications such as wheelchairs or robotic arms do not yet have the reliability essential for use in real life. This is probably the most diffi cult problem”, says Wolpaw. “One of our recent studies suggests that it is possible to get useful control over a long time, but it does not show how reliable this will be for all people with paralysis. This requires more testing”, affi rms Donoghue.

The problems with reliability might be related to unresolved issues. Wolpaw explains: “In the laboratory, monkeys with implanted electrodes or humans wearing EEG electrodes can move robotic arms or control cursors with thought and you can get quite impressive demonstrations. The problem is that none of these methods is reliable enough for real life; their performance varies widely from moment to moment, day to day, and individual to individual and it is not clear why. I think some key basic science issues are yet to be addressed.”

“There are major neuroscience questions that still remain to be answered. We don’t understand everything about what neurons are doing, especially when they are directly related to movement. As we advance in this science we will need more studies to understand what the signals that we interpret as noise are; they could be meaningful”, agrees Donoghue. However, for those BCI applications that do not have a physical risk—eg, sending emails, or browsing the internet—the technology has now entered a new phase. “Today the technologies are mature enough to be brought out of the lab. Why doesn’t it happen? I think it has to do with the commercialisation process, the disabled population is not large enough for it to become interesting to investors”, says Millán. “Ultimately if the technology is successful and we achieve a signifi cant level of control, it could be applied to help people who suff ered a stroke and have lost control of their arm. We are not there yet, but the number of people that have had strokes and are partially paralysed is quite large”, adds Donoghue, whose team has just received approval from the US Food and Drug Administration for a trial of BCI technology in 14 people. The Donoghue laboratory is also working in collaboration with Robert Kirsch from Case Western Reserve University, Cleveland, OH, USA, to develop systems that might allow people with paralysis to move their

own muscles by simply thinking about their movement. Another possibility would be to use BCI technology as an addition or alternative to standard rehabilitation after a stroke, because it might improve the impaired brain’s natural output. However, this potential has not been shown.

BCI technology could also be used in able-bodied people to enhance concentration and attention when driving, for example by using brain signals to activate an alarm when attention starts to lapse; in astronauts to move objects with thought when they are in space; or in gaming or military applications. “Coupling development of BCIs for people who are disabled with development of BCIs for gaming and other purposes that will appeal to larger numbers of people may greatly increase their commercial appeal and viability”, explains Wolpaw. He and his team have also begun a multicentre trial sponsored by the US Veterans Administration that will provide EEG-based home BCI systems to 25 people who are severely disabled by ALS to study the eff ect on their lives and the lives of those close to them.

With such trials and other worldwide eff orts, we hope that a new era for the implementation of BCI technology in people’s lives has now begun.

Patricia Luna

Michele Tavella, a researcher from the École Polytechnique Fédérale de Lausanne (EPFL), demonstrates the use of BCI technology

For more on the Millán team’s non-invasive brain–machine interface see http://cnbi.epfl .ch/

For more on the Donoghue laboratory see http://donoghue.neuro.brown.edu/

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